--- /dev/null
+/*
+ * net/core/dst.c Protocol independent destination cache.
+ *
+ * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ *
+ */
+
+#include <linux/bitops.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/workqueue.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <net/net_namespace.h>
+#include <linux/sched.h>
+#include <linux/prefetch.h>
+
+#include <net/dst.h>
+
+/*
+ * Theory of operations:
+ * 1) We use a list, protected by a spinlock, to add
+ * new entries from both BH and non-BH context.
+ * 2) In order to keep spinlock held for a small delay,
+ * we use a second list where are stored long lived
+ * entries, that are handled by the garbage collect thread
+ * fired by a workqueue.
+ * 3) This list is guarded by a mutex,
+ * so that the gc_task and dst_dev_event() can be synchronized.
+ */
+
+/*
+ * We want to keep lock & list close together
+ * to dirty as few cache lines as possible in __dst_free().
+ * As this is not a very strong hint, we dont force an alignment on SMP.
+ */
+static struct {
+ spinlock_t lock;
+ struct dst_entry *list;
+ unsigned long timer_inc;
+ unsigned long timer_expires;
+} dst_garbage = {
+ .lock = __SPIN_LOCK_UNLOCKED(dst_garbage.lock),
+ .timer_inc = DST_GC_MAX,
+};
+static void dst_gc_task(struct work_struct *work);
+static void ___dst_free(struct dst_entry *dst);
+
+static DECLARE_DELAYED_WORK(dst_gc_work, dst_gc_task);
+
+static DEFINE_MUTEX(dst_gc_mutex);
+/*
+ * long lived entries are maintained in this list, guarded by dst_gc_mutex
+ */
+static struct dst_entry *dst_busy_list;
+
+static void dst_gc_task(struct work_struct *work)
+{
+ int delayed = 0;
+ int work_performed = 0;
+ unsigned long expires = ~0L;
+ struct dst_entry *dst, *next, head;
+ struct dst_entry *last = &head;
+
+ mutex_lock(&dst_gc_mutex);
+ next = dst_busy_list;
+
+loop:
+ while ((dst = next) != NULL) {
+ next = dst->next;
+ prefetch(&next->next);
+ cond_resched();
+ if (likely(atomic_read(&dst->__refcnt))) {
+ last->next = dst;
+ last = dst;
+ delayed++;
+ continue;
+ }
+ work_performed++;
+
+ dst = dst_destroy(dst);
+ if (dst) {
+ /* NOHASH and still referenced. Unless it is already
+ * on gc list, invalidate it and add to gc list.
+ *
+ * Note: this is temporary. Actually, NOHASH dst's
+ * must be obsoleted when parent is obsoleted.
+ * But we do not have state "obsoleted, but
+ * referenced by parent", so it is right.
+ */
+ if (dst->obsolete > 0)
+ continue;
+
+ ___dst_free(dst);
+ dst->next = next;
+ next = dst;
+ }
+ }
+
+ spin_lock_bh(&dst_garbage.lock);
+ next = dst_garbage.list;
+ if (next) {
+ dst_garbage.list = NULL;
+ spin_unlock_bh(&dst_garbage.lock);
+ goto loop;
+ }
+ last->next = NULL;
+ dst_busy_list = head.next;
+ if (!dst_busy_list)
+ dst_garbage.timer_inc = DST_GC_MAX;
+ else {
+ /*
+ * if we freed less than 1/10 of delayed entries,
+ * we can sleep longer.
+ */
+ if (work_performed <= delayed/10) {
+ dst_garbage.timer_expires += dst_garbage.timer_inc;
+ if (dst_garbage.timer_expires > DST_GC_MAX)
+ dst_garbage.timer_expires = DST_GC_MAX;
+ dst_garbage.timer_inc += DST_GC_INC;
+ } else {
+ dst_garbage.timer_inc = DST_GC_INC;
+ dst_garbage.timer_expires = DST_GC_MIN;
+ }
+ expires = dst_garbage.timer_expires;
+ /*
+ * if the next desired timer is more than 4 seconds in the
+ * future then round the timer to whole seconds
+ */
+ if (expires > 4*HZ)
+ expires = round_jiffies_relative(expires);
+ schedule_delayed_work(&dst_gc_work, expires);
+ }
+
+ spin_unlock_bh(&dst_garbage.lock);
+ mutex_unlock(&dst_gc_mutex);
+}
+
+int dst_discard_sk(struct sock *sk, struct sk_buff *skb)
+{
+ kfree_skb(skb);
+ return 0;
+}
+EXPORT_SYMBOL(dst_discard_sk);
+
+const u32 dst_default_metrics[RTAX_MAX + 1] = {
+ /* This initializer is needed to force linker to place this variable
+ * into const section. Otherwise it might end into bss section.
+ * We really want to avoid false sharing on this variable, and catch
+ * any writes on it.
+ */
+ [RTAX_MAX] = 0xdeadbeef,
+};
+
+
+void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
+ int initial_ref, int initial_obsolete, unsigned short flags)
+{
+ struct dst_entry *dst;
+
+ if (ops->gc && dst_entries_get_fast(ops) > ops->gc_thresh) {
+ if (ops->gc(ops))
+ return NULL;
+ }
+ dst = kmem_cache_alloc(ops->kmem_cachep, GFP_ATOMIC);
+ if (!dst)
+ return NULL;
+ dst->child = NULL;
+ dst->dev = dev;
+ if (dev)
+ dev_hold(dev);
+ dst->ops = ops;
+ dst_init_metrics(dst, dst_default_metrics, true);
+ dst->expires = 0UL;
+ dst->path = dst;
+ dst->from = NULL;
+#ifdef CONFIG_XFRM
+ dst->xfrm = NULL;
+#endif
+ dst->input = dst_discard;
+ dst->output = dst_discard_sk;
+ dst->error = 0;
+ dst->obsolete = initial_obsolete;
+ dst->header_len = 0;
+ dst->trailer_len = 0;
+#ifdef CONFIG_IP_ROUTE_CLASSID
+ dst->tclassid = 0;
+#endif
+ atomic_set(&dst->__refcnt, initial_ref);
+ dst->__use = 0;
+ dst->lastuse = jiffies;
+ dst->flags = flags;
+ dst->pending_confirm = 0;
+ dst->next = NULL;
+ if (!(flags & DST_NOCOUNT))
+ dst_entries_add(ops, 1);
+ return dst;
+}
+EXPORT_SYMBOL(dst_alloc);
+
+static void ___dst_free(struct dst_entry *dst)
+{
+ /* The first case (dev==NULL) is required, when
+ protocol module is unloaded.
+ */
+ if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) {
+ dst->input = dst_discard;
+ dst->output = dst_discard_sk;
+ }
+ dst->obsolete = DST_OBSOLETE_DEAD;
+}
+
+void __dst_free(struct dst_entry *dst)
+{
+ spin_lock_bh(&dst_garbage.lock);
+ ___dst_free(dst);
+ dst->next = dst_garbage.list;
+ dst_garbage.list = dst;
+ if (dst_garbage.timer_inc > DST_GC_INC) {
+ dst_garbage.timer_inc = DST_GC_INC;
+ dst_garbage.timer_expires = DST_GC_MIN;
+ mod_delayed_work(system_wq, &dst_gc_work,
+ dst_garbage.timer_expires);
+ }
+ spin_unlock_bh(&dst_garbage.lock);
+}
+EXPORT_SYMBOL(__dst_free);
+
+struct dst_entry *dst_destroy(struct dst_entry * dst)
+{
+ struct dst_entry *child;
+
+ smp_rmb();
+
+again:
+ child = dst->child;
+
+ if (!(dst->flags & DST_NOCOUNT))
+ dst_entries_add(dst->ops, -1);
+
+ if (dst->ops->destroy)
+ dst->ops->destroy(dst);
+ if (dst->dev)
+ dev_put(dst->dev);
+ kmem_cache_free(dst->ops->kmem_cachep, dst);
+
+ dst = child;
+ if (dst) {
+ int nohash = dst->flags & DST_NOHASH;
+
+ if (atomic_dec_and_test(&dst->__refcnt)) {
+ /* We were real parent of this dst, so kill child. */
+ if (nohash)
+ goto again;
+ } else {
+ /* Child is still referenced, return it for freeing. */
+ if (nohash)
+ return dst;
+ /* Child is still in his hash table */
+ }
+ }
+ return NULL;
+}
+EXPORT_SYMBOL(dst_destroy);
+
+static void dst_destroy_rcu(struct rcu_head *head)
+{
+ struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
+
+ dst = dst_destroy(dst);
+ if (dst)
+ __dst_free(dst);
+}
+
+void dst_release(struct dst_entry *dst)
+{
+ if (dst) {
+ int newrefcnt;
+
+ newrefcnt = atomic_dec_return(&dst->__refcnt);
+ WARN_ON(newrefcnt < 0);
+ if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt)
+ call_rcu(&dst->rcu_head, dst_destroy_rcu);
+ }
+}
+EXPORT_SYMBOL(dst_release);
+
+u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old)
+{
+ u32 *p = kmalloc(sizeof(u32) * RTAX_MAX, GFP_ATOMIC);
+
+ if (p) {
+ u32 *old_p = __DST_METRICS_PTR(old);
+ unsigned long prev, new;
+
+ memcpy(p, old_p, sizeof(u32) * RTAX_MAX);
+
+ new = (unsigned long) p;
+ prev = cmpxchg(&dst->_metrics, old, new);
+
+ if (prev != old) {
+ kfree(p);
+ p = __DST_METRICS_PTR(prev);
+ if (prev & DST_METRICS_READ_ONLY)
+ p = NULL;
+ }
+ }
+ return p;
+}
+EXPORT_SYMBOL(dst_cow_metrics_generic);
+
+/* Caller asserts that dst_metrics_read_only(dst) is false. */
+void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
+{
+ unsigned long prev, new;
+
+ new = ((unsigned long) dst_default_metrics) | DST_METRICS_READ_ONLY;
+ prev = cmpxchg(&dst->_metrics, old, new);
+ if (prev == old)
+ kfree(__DST_METRICS_PTR(old));
+}
+EXPORT_SYMBOL(__dst_destroy_metrics_generic);
+
+/* Dirty hack. We did it in 2.2 (in __dst_free),
+ * we have _very_ good reasons not to repeat
+ * this mistake in 2.3, but we have no choice
+ * now. _It_ _is_ _explicit_ _deliberate_
+ * _race_ _condition_.
+ *
+ * Commented and originally written by Alexey.
+ */
+static void dst_ifdown(struct dst_entry *dst, struct net_device *dev,
+ int unregister)
+{
+ if (dst->ops->ifdown)
+ dst->ops->ifdown(dst, dev, unregister);
+
+ if (dev != dst->dev)
+ return;
+
+ if (!unregister) {
+ dst->input = dst_discard;
+ dst->output = dst_discard_sk;
+ } else {
+ dst->dev = dev_net(dst->dev)->loopback_dev;
+ dev_hold(dst->dev);
+ dev_put(dev);
+ }
+}
+
+static int dst_dev_event(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+ struct dst_entry *dst, *last = NULL;
+
+ switch (event) {
+ case NETDEV_UNREGISTER_FINAL:
+ case NETDEV_DOWN:
+ mutex_lock(&dst_gc_mutex);
+ for (dst = dst_busy_list; dst; dst = dst->next) {
+ last = dst;
+ dst_ifdown(dst, dev, event != NETDEV_DOWN);
+ }
+
+ spin_lock_bh(&dst_garbage.lock);
+ dst = dst_garbage.list;
+ dst_garbage.list = NULL;
+ spin_unlock_bh(&dst_garbage.lock);
+
+ if (last)
+ last->next = dst;
+ else
+ dst_busy_list = dst;
+ for (; dst; dst = dst->next)
+ dst_ifdown(dst, dev, event != NETDEV_DOWN);
+ mutex_unlock(&dst_gc_mutex);
+ break;
+ }
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block dst_dev_notifier = {
+ .notifier_call = dst_dev_event,
+ .priority = -10, /* must be called after other network notifiers */
+};
+
+void __init dst_init(void)
+{
+ register_netdevice_notifier(&dst_dev_notifier);
+}
Code Review / kvmfornfv.git / blobdiff